Hidden Magma Flow Triggered Santorini Quakes, New Research Finds
A recent wave of quakes that shook the Greek island of Santorini earlier this year has been linked to underground volcanic activity, with scientists pointing to a hidden magma flow as the cause of the month-long unrest.
The discovery challenges earlier assumptions that the tremors were related to fault lines, offering new insight into how magma flow may have sparked the Santorini quakes.
The seismic swarm began with little warning, rattling the island with thousands of small quakes over several weeks. At times, the ground shook every few minutes. The strongest event reached a magnitude of 5.3. More than 10,000 people were forced to evacuate their homes, while scientists raced to determine the cause.
But for University of Oregon geophysicist Emilie Hooft, the timing was more than a coincidence. Just 10 days before the shaking began, her team had submitted a study identifying a deep volcanic structure beneath the island, based on seismic imaging collected during a multi-year research project.
New research challenges fault-based theories
Unlike the typical volcanic activity seen directly beneath mountain peaks, Hooft’s findings revealed something different: magma movement occurring 6 to 9 miles below the surface, but offset from Santorini’s known volcanoes.
“We found magma at deeper depths that is offset from both the main volcano and from the active volcanic seamount 10 kilometers (6 miles) to the northeast,” Hooft said. The earthquakes, she explained, lined up with a newly identified region of deep magma storage. That’s where the seismic activity began.
The research, published in Geochemistry, Geophysics, Geosystems, is based on two major studies led by Hooft and her doctoral students. One study, led by Beck Hufstetler, used sound waves to estimate the amount of molten rock beneath the crust.
The second, led by Kaisa Autumn, mapped the deeper layers using reflected sound waves. Her findings pinpointed the exact region where magma was pushing sideways through the crust—the same area where the quakes later erupted.
Sideways magma flow could redefine risk zones
Previous models assumed magma rose vertically beneath volcanic peaks. However, Hooft’s team found that it often travels through cracks and faults, moving horizontally before surfacing—or not surfacing at all.
“Our research reinforces a growing view that volcanic unrest shouldn’t be considered in isolation, but as part of a complex, evolving system of magma, fault, and crust,” Hooft said.
“Magma movement is often guided by structural features of the crust, like cracks in the fault system, which means future volcanic unrest may occur outside traditional volcanic centers.”
Hooft began studying Santorini’s volcanic system in 2015. She led one of the largest seismic imaging missions ever conducted on a volcano.
For nearly a month, her international team sent sound waves through the seafloor, collecting data around the clock to map what lies deep beneath the island.
Imaging tools reveal deeper secrets of the crust
The team used pulses of compressed air to create sound waves that work like an ultrasound. These waves revealed layers of rock, lava, and trapped water, helping scientists build the clearest picture yet of the island’s volcanic plumbing system.
Until recently, research in the area was limited to the upper 3 to 4 miles of the crust. But the new data allowed Hooft’s team to explore much deeper, down to nearly 15 miles.
The discovery that magma is traveling sideways through offset cracks—rather than rising directly beneath visible volcanoes—could help researchers better anticipate future volcanic threats in the region.
“Understanding how and when magma moves through these systems remains one of the central challenges in volcanic science and a critical step toward detecting early warning signs and improving hazard assessment in vulnerable regions like the southern Aegean,” Hooft said.
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